Intelligent I O

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Advanced rugged nanosized Intelligent I/O™ and communications subsystem from North Atlantic Industries (NAI) delivers significant advantages for mission computers in airborne vehicles The Nano Interface Unit (NIU1) adds distributed network sensor data interfaces to airborne mission computer without expensive chassis or backplane redesign.

Nanosized intelligent I/O™ communications subsystems

Intelligent I/O Intelligent Image Database System Intelligent Image Quality Intelligent Image Stabilization Intelligent Inference Systems Corporation Intelligent Information Agents Workshop Intelligent Information Handler Intelligent Information Hiding and Multimedia Signal Processing intelligent information management.

Networked, Intelligent I/O Jim Pinto

IntroductionDeterministic Systems vs Autonomous AgentsThe ASIC RevolutionPhysical PackagingI/O NetworksFault Tolerant & FailSafeIntelligent I/O Control SystemsDistributed Autonomous IntelligenceI/O typically refers to measurements that are “subservient” to the central computer or controller with minimal “intelligence” at the I/O point The term “smart” I/O was coined for I/O with at least minimal local memory and processing capabilities for example keeping the output at a fixed level when communications are lost In computerbased systems with remote I/O control typically cannot be done in the central computer since loss of communications would result in loss of control Therefore full PID type local controllers are used for closedloop control supervised by the remote computer The computer is relegated to supervisory tasks such as modification or adjustment of setpoints and control parameters This is an expensive alternative but accepted as necessary The two largest segments of industrial measurement & control systems are PLC (programmable logic controllers) and DCS (Distributed Control Systems) Other market segments such as SCADA (Supervisory Control and Data A hierarchical control system is subject to complex software constraints network communication conflicts and networkspeed limitations The upperlimits of I/O count capability for conventional DCS and PLC systems appears to be limited only by datarates however it is almost selfevident that the maximum I/O count is primarily limited by sheer complexity issues and secondarily by cost The practical I/O count for programmable intelligent networked “autonomous agents” greatly exceeds that limit Intelligent I/O with algorithmic response mechanisms has no theoretical complexity limit The author theorizes that DCS systems are indeed theoretically limited because of complexity Several major DCS and PLC manufacturers have been asked directly about the maximum number of I/O controlled by current systems with a number in the region of 30000 typically at a cost of several million $ Honeywell has achieved a pointcount of 80000 in the SASOL project in South Africa but this Three siliconchip developments have contributed to the new I/O architecture to achieve practical cost/performance/complexity which compares with conventional block I/O based system Figure 1 Intelligent I/O modules built within a standard terminalblock package By contrast a trulydistributed I/O system would include ASICchip based electronics directly within a terminalblock housing (Figure 1) The singlepoint input or output point would be connected directly to the nearest available network access via 2wires The vast conglomeration and complexity of wiring is eliminated providing vastly improved reliability aside from other less obvious advantages In March &#3994 at the ICEE in Chicago two major new networked industrial I/O systems were introduced DeviceNet™ by AllenBradley and SDS™ (Smart Distributed System) by Honeywell Micro Switch Both were beyond just proprietary product launches and were startlingly similar in that both were based on CAN the Control Area Network chip and both claimed to provide a platform for open and interoperableindustrial networking strongly soliciting thirdparty vendor involvement and support (Ref 4) Networking on the factory floor is advancing inexorably because of the many benefits it brings Networked device installation is much more costeffective than traditional I/O wiring in most applications and allows much improved maintenance a device may be removed or replaced without shutting down other devices in the same system An open device network will quickly provide common solutions reducing the need to support a wide variety of devices and networks currently proliferating in t A significant problem occurs when dependent I/O is separated from the central processor If the connections are cut the I/O becomes relatively incompetent SmartI/O supposedly overcomes this problem but the intelligence is usually limited to holding an output to a predetermined value while waiting for the connection to be reestablished With the type of intelligent programmable I/O systems being described faulttolerance is achieved by simple duplication (or even triplication) of the measurement and control where it occurs Loss of communications with the host or even between I/O points simply transfers control to a local tolerance algorithm processed independently within the I/O modules The concept of a faulttolerant computer becomes irrelevant when the I/O itself is faulttolerant This is a significant advantage With autonomous agent I/O systems the system design is robust as opposed to brittle Fault tolerant or Failsafe operation in a system of this type has severa Figure 2 Control system based on networked single point autonomousI/O modules The input modules are near the sensors and the outputs near the actuators Take the example of a PID controller conventionally a single panelmounted instrument with adjustable setpoint and control parameters (PID) and displays of input output and setpoint Typically the input and output would need to be wired to this instrument With the networked I/O architecture being described the input module would be located near the sensor the setpoint module (potentiometer adjustment) would be at a location convenient for the operator and the output module (perhaps 420mA) would be near the actuator (pneumatic valve) There would be no mechanical PID adjustment potentiometers since these parameters are simply nonvolatile memoryadjustments within the output module adjustable from an operators computer console The three networked modules (input setpoint and output) would be boundtogethe A network of taxis is an excellent metaphorical illustration of how a chicken brain control system would work Each taxi (node) is completely independent with at least some minimal intelligence Network communication is via a radio link Programming is rulebased and relatively simple so that a novice is easily instructed on the protocol to follow Each taxi reports within predetermined rules timebased if there is no incident to report or eventbased in a changing situation Typical response time (to order and have a taxi arrive) may be a few minutes one cannot guarantee which taxi responds but speedy response is guaranteed If the radiolink is interrupted for any reason an individual taxi follows preagreed backup rules to continue operation When communication is restored improved networkoperation continues Faulttolerance and redundancy rules are simple extensions If a specific taxi breaks down during the assignment another taxi can immediately be called up withi.